This Proposal consists of nine projects which relate to the structure and function of the gastrointestinal tract and to the pathogenesis of its diseases. The following topics will be studied: 1) how luminal phospholipids influence fat absorption, 2) how rates of fatty acid absorption determine their route of transport from the small intestine, 3) what luminal factors influence synthesis and release of chylomicrons, 4) immunochemistry and immunomorphology of intestinal lipoproteins, 5) influence of luminal pH on absorption of water and solute, 6) mechanisms by which Ca ions and Mg ions alter intestinal absorptive cell function, 7) role of extracellular leaks in the pathogenesis of secretory diarrhea, 8) effect of chronic laxative use on colonic structure and function, 9) the structure and function of the gastro-intestinal tract in disorders of propulsion.